True romance ... a still from Mia Hansen-Løve's Un Amour de Jeunesse (Goodbye First Love)

Of all film festivals, Locarno's is the most magical. You can't forget starlit nights spent amid an 8,000-strong crowd in front of a huge screen in the historic Piazza Grande. Nor the casual encounters with stars, directors and fellow-fans that often accompany a stroll between screenings across the campus-like Spaziocinema. Still, often magic is not enough, and in recent years a trip to the Swiss lakeside town has been seen as a jolly for self-satisfied Euro cineastes. Now, however, things are changing.

Director Olivier Père is out to streamline and beef up the £8.2m event by rediscovering its knack for blending new, forgotten or esoteric work with mainstream populist fare. This year, that means a cutting-edge international competition with 14 world premieres, including those of Nicolas Klotz's Low Life, about an Afghan asylum-seeker in love; Sebastián Lelio's El Año del Tigre, a Chilean post-apocalyptic saga; and Tawfik Abu Wael's Tanathur, a study of the angst of a privileged Palestinian couple. Another strand promoting first and second features boasts plenty of ambitious-looking efforts, particularly from Asia. There's also an attempt to boost non-Bollywood Indian output with a co-production marketplace for 12 selected projects.

Last night, actor Leslie Caron was on the Piazza to introduce a Vincente Minnelli retrospective featuring 33 of his films. Also in town will be Claudia Cardinale, Gérard Depardieu, Hitoshi Matsumoto, Bruno Ganz, Abel Ferrara, Kabir Bedi, Claude Goretta, Mike Medavoy, Anri Sala and Isabelle Huppert, who will receive the festival's Excellence award.

Hollywood blockbusters are also now part of the mix. The festival's opener was JJ Abrams's Super 8. Sadly, none of the stars showed up, pleading location duties. Saturday's screening of Cowboys and Aliens has more star-power – it will be introduced by Daniel Craig, Harrison Ford, Olivia Wilde and director Jon Favreau.

Though this prospect has added an element of glitz to the proceedings, the essence of Locarno is still in the showcase it provides for fresh, thoughtful European arthouse titles – such as today's Un Amour de Jeunesse (Goodbye First Love in the UK), a widely-tipped candidate for the international competition's Golden Leopard. This is the third feature in a semi-autobiographical series directed by 30-year-old Parisienne Mia Hansen-Løve, a festival favourite who cut her teeth beside Lake Maggiore with a well-received short in 2003. Her last film, Le Père de Mes Enfants (The Father of My Children), secured five stars from The Guardian's Peter Bradshaw.

Hansen-Løve has moved on from her preoccupation with partner issues. It's Paris, 1999. Fifteen-year-old Camille is mousy, sulky and studious, but so perfectly formed that she easily snares a curly-haired, 19-year-old Adonis called Sullivan. They enjoy a summer of love, but then Sullivan heads off alone for a 10-month backpacking trip around South America. His letters dry up. Camille can't get over him and attempts to commit suicide. Four years later, she moves in with a more grounded older man. They're getting on fine, but then Sullivan reappears on the scene. So far, so The Umbrellas of Cherbourg, but unlike Catherine Deneuve's Geneviève, Lola Créton's Camille resumes the dangerous liaison of her romantic infancy …

Camille's mindset is convincingly rendered. Desperate to swamp her adolescent disquiet in a grand passion, she pesters Sebastian Urzendowsky's flighty Sullivan with a charmless barrage of clingy, passive-aggressive complaints, demands and suicide threats. His desire to escape is all too blatant. So is his comeback attempt. Camille's fixation on avoiding her issues by becoming involved with successive men is recognisable enough, as is her willingness to betray them when her mission requires it.

Cinematographer Stéphane Fontaine invests the nondescript suburbs of Paris with nervy foreboding and sobers up what would otherwise be a hackneyed away-break idyll in the leafy Ardèche. Both the principals turn in sturdy performances. The dialogue seems stilted and gauche, but that's probably appropriate for the kind of exchanges that are generally taking place.

The real problem, however, is that Camille just isn't engaging enough to merit our attention for the full 110 minutes. Geneviève was also a pretty uncomplicated girl, but between them Deneuve, Jacques Demy and Michel Legrand manage to invest her fate with an aura of significance that seems beyond Hansen-Løve's capacity. Still, it will be worth waiting for her next film, and Locarno is likely to be the best place to catch it.

If the jury also find something lacking in Un Amour de Jeunesse, it's still possible that the Leopard will be carried off by a woman. Also fancied in a strong field for female auteurs are Danielle Arbid's Beirut Hotel, a Lebanon-based love story laced with intrigue and violence; Anca Damian's Crulic - drumul spre dincolo, an animated documentary narrated from beyond the grave by an unjustly jailed Romanian hunger-striker; and Julia Loktev's The Loneliest Planet, which deals with an engaged couple's ill-fated trek into the Georgian Caucasus mountains.